Airborne hyperspectral cameras provide the basic information to estimate the energy wasted skywards by outdoor lighting systems, as well as to locate and identify their sources. However, a complete characterization of the urban light pollution levels also requires evaluating these effects from the city dwellers standpoint, e.g. the energy waste associated to the excessive illuminance on walls and pavements, light trespass, or the luminance distributions causing potential glare, to mention but a few. On the other hand, the spectral irradiance at the entrance of the human eye is the primary input to evaluate the possible health effects associated with the exposure to artificial light at night, according to the more recent models available in the literature. In this work we demonstrate the possibility of using a hyperspectral imager (routinely used in airborne campaigns) to measure the ground-level spectral radiance of the urban nightscape and to retrieve several magnitudes of interest for light pollution studies. We also present the preliminary results from a field campaign carried out in the downtown of Barcelona.

Urban systems are known to have a number of effects on avian diversity, density, and morphological and behavioral traits. However, no study to date has simultaneously examined the wide range of urban variables in relation to the avian dawn chorus, a complex behavioral phenomenon. Previous studies investigating adjustments of the dawn chorus onset in urban settings have mainly been confined to relationships with noise and light levels. In addition to noise and light levels, in this study we included other potentially related environmental characteristics describing vegetation structure, urban infrastructure, and human activity, all of which have been shown to be drivers of bird diversity in urban areas. We conducted dawn chorus surveys at 38 Los Angeles urban greenspaces and used a classification and regression tree analysis to identify specific urban scenarios that best explained timing differences in the dawn chorus onset. Our results show that light level was the most important determinant of the dawn chorus onset time, in which, counter-intuitively, bird communities in greenspaces with higher light levels had later onsets. In addition, noise was an important factor for the chorus onset in greenspaces with higher light levels. Although our results differ from those of previous studies, these findings highlight the importance of noise and light levels in explaining dawn chorus onset variation, indicating the need for further research in untangling this complex and ecologically important phenomenon.

Patients with Huntington's disease (HD) exhibit movement disorders, psychiatric disturbance and cognitive impairments as the disease progresses. Abnormal sleep/wake cycles are common among HD patients with reports of delayed sleep onset, fatigue during the day, and a delayed pattern of melatonin secretion all of which suggest circadian dysfunction. Mouse models of HD confirm disrupted circadian rhythms with pathophysiology found in the central circadian clock (suprachiasmatic nucleus). Importantly, circadian dysfunction manifests early in disease, even before the classic motor symptoms, in both patients and mouse models. Therefore, we hypothesize that the circadian dysfunction may interact with the disease pathology and exacerbate the HD symptoms. If correct, early intervention may benefit patients and delay disease progression. One test of this hypothesis is to determine whether light therapy designed to strengthen this intrinsic timing system can delay the disease progression in mouse models. Therefore, we determined the impact of blue wavelength-enriched light on two HD models: the BACHD and Q175 mice. Both models received 6 hours of blue-light at the beginning of their daily light cycle for 3 months. After treatment, both genotypes showed improvements in their locomotor activity rhythm without significant change to their sleep behavior. Critically, treated mice of both lines exhibited improved motor performance compared to untreated controls. Focusing on the Q175 genotype, we sought to determine whether the treatment altered signaling pathways in brain regions known to be impacted by HD using NanoString gene expression assays. We found that the expression of several HD relevant markers was altered in the striatum and cortex of the treated mice. Our study demonstrates that strengthening the circadian system can delay the progression of HD in pre-clinical models. This work suggests that lighting conditions should be considered when managing treatment of HD and other neurodegenerative disorders.

Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are grounded by lights when they fly at night. We review the current state of knowledge of light attraction, identify information gaps and propose measures to address the problem. Although other avian families such as Alcidae and Anatidae can be involved, the most affected seabirds are petrels and shearwaters: at least 56 species, more than one-third of them (24) threatened, are grounded by lights. Grounded seabirds have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding grounds confined to formerly uninhabited islands are particularly at risk from ever-growing levels of light pollution due to tourism and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the most immediate and extended mitigation measures to reduce light-induced mortality, saving thousands of birds every year. These programs also provide useful information for seabird management. However, the data typically are fragmentary and often strongly biased so the phenomenon is poorly understood, leading to inaccurate impact estimates. We identified as the most urgent priority actions: 1) estimation of mortality and impact on populations; 2) assessment of threshold light levels and safe distances from light sources; 3) documenting the fate of rescued birds; 4) improvement of rescue campaigns, particularly in terms of increasing recovery rates and level of care; and 5) research on seabird-friendly lights to reduce attraction. More research is necessary to improve our understanding of this human-wildlife conflict and to design effective management and mitigation measures. This article is protected by copyright. All rights reserved.

Reduced exposure to daytime sunlight and increased exposure to electrical lighting at night leads to late circadian and sleep timing [1-3]. We have previously shown that exposure to a natural summer 14 hr 40 min:9 hr 20 min light-dark cycle entrains the human circadian clock to solar time, such that the internal biological night begins near sunset and ends near sunrise [1]. Here we show that the beginning of the biological night and sleep occur earlier after a week's exposure to a natural winter 9 hr 20 min:14 hr 40 min light-dark cycle as compared to the modern electrical lighting environment. Further, we find that the human circadian clock is sensitive to seasonal changes in the natural light-dark cycle, showing an expansion of the biological night in winter compared to summer, akin to that seen in non-humans [4-8]. We also show that circadian and sleep timing occur earlier after spending a weekend camping in a summer 14 hr 39 min:9 hr 21 min natural light-dark cycle compared to a typical weekend in the modern environment. Weekend exposure to natural light was sufficient to achieve approximately 69% of the shift in circadian timing we previously reported after a week's exposure to natural light [1]. These findings provide evidence that the human circadian clock adapts to seasonal changes in the natural light-dark cycle and is timed later in the modern environment in both winter and summer. Further, we demonstrate that earlier circadian timing can be rapidly achieved through natural light exposure during a weekend spent camping.